Intercomparison of absorbed dose to water measurements for 60Co gamma rays using Fricke, alanine and radiochromic dye film dosimetry.

Measurements of absorbed dose at 5 cm depth in a 30 x 30 x 30 cm3 water phantom have been performed using three independent dosimetric techniques: Fricke, alanine and radiochromic dye film (GafChromic HD-810). The measurements were carried out in the secondary standard dosimetry laboratory at ININ Mexico using a collimated 60Co gamma source with a radiation field of 10 x 10 cm2 at the phantom front surface. The source to phantom distance was set at 100 cm. The reference absorbed dose at 5 cm depth in the water phantom was obtained using a 0.6 cm3 ionisation chamber. The absorbed dose to water for the test dosimetry techniques was around 100 Gy. The deviations of the dose obtained from these dosimetry techniques were within 4%. The reasons for these deviations are discussed.